Biology subjects

Rault, L.

Publications and source records attributed to Rault, L..

3 recordsLinked to original sources

bioRxiv2025

Human milk bacteria assembled into functionally distinct synthetic communities in infant formula differently affect intestinal physiology and microbiota in neonatal mini-piglets

The contribution of Human milk (HM) microbiota to infant gut health was addressed by evaluating the impact of HM bacteria, combined in two synthetic communities (SynComs) exhibiting anti-inflammatory (AI) or high immunomodulatory (HI) properties in vitro, on gut immune and barrier functions, and microbiota. Neonatal mini-piglets were fed either a formula without supplementation (CTRL) or supplemented with AI or HI SynComs, and were compared to sow milk-fed (SM) piglets over a period of 24 days. Feces were collected on postnatal day (PND) 8, and ileal, colonic and fecal samples were collected on PND24. The multifactorial analysis indicated that the two HM-derived SynComs impacted microbiota and intestinal functions differently. Several genera, mainly belonging to Bacillota, displayed different relative abundances between the formula-fed groups at both PND8 and PND24. At PND8, the fecal sIgA level in HI piglets was slightly lower than in SM piglets but markedly higher than in CTRL and AI piglets. SynComs HI and/or AI slightly increased the expression of genes involved in pro-inflammatory (IL6, TNFaR1), antioxidant (SOD2), anti-inflammatory (SOCS3) and Treg (FOXP3) pathways in ileal and colonic tissues compared with the CTRL group. Systemic immune functions were also modulated with a cytokine secretion capacity of peripheral blood mononuclear cells that tended to be higher with HI supplementation. Interestingly, SynCom bacteria were correlated with several ileal and colonic genera, and both were correlated with physiological variables. Overall, our findings support the influence of HM bacteria, provided in formulas as SynCom at a physiological concentration, on gut microbiota and functions. ImportanceEarly-life environmental factors, such as neonatal diet, influence the gut microbiota, which plays a key role in the functional development of the gut. However, the role of the human milk (HM) microbiota, particularly with regard to the immunomodulatory properties of HM bacteria, is not well understood. This study investigates the differential effects of two synthetic communities with a similar taxonomic composition representative of the taxonomic diversity of the HM microbiota. Thse communities exhibit contrasting immunomodulatory properties that were previously characterized using an in vitro intestinal quadricellular model. Daily supplementation with these two SynComs modulated the composition of the gut microbiota and the gut physiology differently, particularly the intestinal immune signatures. In conclusion, the functional profile of bacteria within the HM microbiota may induce distinct developmental profiles of gut physiology in infants.

physiology↗

bioRxiv2024

New insights into the cultivability of human milk microbiota from ingestion to digestion and implications for its immunomodulatory properties

Human milk (HM) microbiota is increasingly studied for its potential health benefits. However, the physiological state of HM bacteria and consequently their effects on gut homeostasis remain a question. This study investigated the physiological state of the HM microbiota by characterizing its cultivable fraction, as it might be at the point of ingestion and assessing the effects of digestion on the cultivability and immunomodulatory properties of six prevalent HM strains. The microbiota of 28 HM samples was analysed by 16S metabarcoding either directly on raw milk (raw milk microbiota, RM) or on the complete cultivable fraction obtained from seven non-selective media (cultivable milk microbiota, CM). Diversity was lower in CM than in RM, with 32 versus 435 genera and a median of 7 versus 69 genera per sample in CM and RM, respectively. CM also showed under-representation of strictly anaerobic genera. Factors like parity and iron or vitamin supplementation affected RM and/or CM. In vitro gastrointestinal digestion moderately impacted strain cultivability. However, most strains partially or completely lost their immunomodulatory properties on the monocyte THP1 cell line after digestion, except a Staphylococcus epidermidis strain that gained immunomodulatory potential.

microbiology↗

bioRxiv2024

Development of a competition assay to assess the in vitro fitness of dengue virus serotypes using an optimized serotype-specific qRT-PCR

BackgroundComparing the in vitro fitness of dengue virus (DENV) isolates is a pivotal approach to assess the contribution of DENV strains replicative fitness to epidemiological contexts, including serotype replacements. Competition assays are the gold standard to compare the in vitro replicative fitness of viral strains. Implementing competition assays between DENV serotypes requires an experimental setup and an appropriate read-out to quantify the viral progeny of strains belonging to different serotypes. ResultsIn the current study, we optimized an existing serotyping qRT-PCR by adapting primer/probe design and multiplexing the serotype-specific qRT-PCR reactions, allowing to accurately detect and quantify all four DENV serotypes. The qRT-PCR was specific, had a limit of detection of at least 5.08x101, 5.16x101, 7.14x101 and 1.36 x101 genome copies/{micro}L, an efficiency of 1.993, 1.975, 1.902, 1.898 and a linearity (R{superscript 2}) of 0.99975, 0.99975, 0.9985, 0.99965 for DENV-1, -2, -3 and -4 respectively. Challenge of this multiplex serotype-specific qRT-PCR on mixes of viral supernatants containing known concentrations of strains from two serotypes evidenced an accurate quantification of the amount of genome copies of each serotype. We next developed an in vitro assay to compare the replicative fitness of two DENV serotypes in the human hepatic cell line HuH7: quantification of the viral progeny of each serotype in the inoculum and the supernatant using the serotype-specific multiplex qRT-PCR unveiled an enrichment of the supernatant in DENV-1 genome copies, uncovering the enhanced replicative fitness of this DENV-1 isolate. ConclusionsThis optimized qRT-PCR combined to a relevant cellular model allowed to accurately quantify the viral progeny of two DENV strains belonging to two different serotypes in a competition assay, allowing to determine which strain had a replicative advantage. This reliable experimental setup is adaptable to the comparative study of the replicative fitness of any DENV serotypes.

microbiology↗